Distributed Temperature Sensing (DTS) devices are optoelectronic devices which measure temperature by optical fibers functioning as linear sensors. Temperature values are recorded along the optical sensor cable as a continuous profile. A high accuracy of temperature determination is achieved over long distances. Measurement distances of several kilometers can be achieved. The temperature dependence of the Raman effect can be used for a DTS measurement.
In DTS and other distributed fiber sensing technologies, a fiber under test can be probed by sending single pulses or sequences of pulses or pulse trains of light into the fiber. Backscattered light can be analyzed and spatially resolved for different physical properties of the fiber. For instance, Raman-backscatter gives information on temperature, Brillouin-scattered light contains information on temperature and strain and Rayleigh scattered light can be analyzed for losses and reflective sections of the fiber (e.g., using optical time domain reflectometry (OTDR)) or can be used for distributed acoustic sensing (e.g., using coherent optical time domain reflectometry (C-OTDR)). To achieve sufficient spatial resolution, the outgoing pulse has to generate backscatter at a limited spatial region for a distinct time, this requires production of short pulses. If the returning signal is resolved temporally, it is possible to obtain a distributed measurement signal over time.
An approach that increases signal-to-noise ratio without increasing peak light power and without affecting the spatial resolution of the acquired signal is sending pulse trains which represent a code with suitable properties, as an example but not limited to Golay codes, Barker codes, or simplex codes.
Artifacts in pulse generation may result in artifacts in measurement data.
EP 2,775,278 discloses an optical fiber temperature distribution measurement device for measuring a temperature distribution along a longitudinal direction of an optical fiber. The device includes a light transmitter configured to input a train of code-modulated light pulses into the optical fiber, a light receiver configured to receive Raman back scattering light generated by inputting the train of code-modulated light pulses into the optical fiber, a demodulator configured to perform a correlation processing between a measured signal output from the light receiver and a code string associated with a type of the code modulation performed by the light transmitter, and to demodulate the measured signal. A data store is provided for storing correction data to be used to correct a distortion of the measured signal output from the light receiver when an impulsive pulsed light is output from the light transmitter. A corrector is configured to perform a correction to one of the measured signal output from the light receiver and a demodulated signal output from the demodulator, using the correction data stored in the data store.